318 BROWN & HERON: GEOLOGY AND ORE DEPOSITS OF TAVOY. 



picked clean and the fines rewashed. hi weighing, a specially 

 devised set of Weights is used, the unit of which, weighing 70 grains, 

 corresponds to 1 lb. per cubic yard. The weights extend from 

 3 grains (0*05 lb.), up to 7,000 grains (100 lbs.). Thus the value 

 of the concentrate is read off directly in pounds per cubic yard.'' 1 



Hydraulic Mining, Sluicing and Pumping. 



In a climate like the Tavoy one the quartz veins undergo rapid 

 denudation and shed their contents into the surface soil. Valuable 

 deposits are thus formed, consisting of wolfram and cassiterite in 

 the surface covers of the hill sides and of cassiterite in the true water- 

 sorted alluvium of the valleys. In the early days of the industry 

 the greater part of the output was won by ground-sluicing rich patches 

 of detrital or eluvial ground on the slopes of the hills when water was 

 available in the rainy seasons. Much of this early work was done in 

 a very haphazard fashion, but in more recent times with Chinese, 

 who are the best sluicers, with efficient management and with im- 

 proved arrangements for bringing in water and recovering the ores, 

 considerable improvements have been effected. Now-a-days on a large 

 mine like Hermyingyi, the Chinese workmen are compelled to use 

 standard boxes for which timber is provided, and definite claims are 

 distributed on the understanding that, if the tributors concerned fail 

 to operate them properly, or if they stack waste stones on unworked 

 ground—a common Chinese failing — they will be forfeited. 



It was not long before it was realised that the detrital deposits 

 of the slopes and the mixed detrital and alluvial deposits at the 

 foot of the hills could in many places be worked to advantage with 

 monitors and hydraulic appliances generally, and hydraulic sluicing 

 was first introduced about 1912. Plants of this kind are now in 

 operation at Kanbauk, Hermyingyi, Wagon, Pagaye, Widnes and 

 other mines. 



In the first stages of a mine's history the beds and banks of the 

 streams are the first to be cleaned up by tributors, and it may be 

 taken for granted that their methods result in very serious loss 

 unless closely supervised, especially as regards the waste of fine con- 

 centrates and the covering up of bearing ground with tailings. 

 Profitable ground lying at a higher level may then be discovered, when 

 surveys of the surrounding natural water systems are necessary to 



1 H. E. Hooper, Eng and Min. Journ., Vol. 102, No. 5, July 29th, 1916. 



